Parametric study is a useful method for exploring alternative design options and establishing dependencies between design variables. The development of an open-source research tool, jEPlus, has been reported in 2009. The tool is designed to assist setting up parametric runs with EnergyPlus models, and to perform the simulations in “parallel” mode. This paper uses an example to demonstrate how jEPlus can be used for setting up complex parametric runs. In the example, four different building types and five HVAC system configurations were considered along with design parameters including insulation, glazing, temperature set points and day lighting control options. Further more, the simulations were carried out in three different climatic regions. Given that the total number of simulations exceeds 30,000, it would have been a tedious, if not impossible, job to set them up manually. jEPlus made it trivial, however, by automating the tasks such as generating input files for EnergyPlus, executing simulations, and extracting results.